Fritz,
Ok, i admit, that was a noobie thing, that worked.
Next move:
sudo dpkg -i mpv_0.14.0_armhf.deb
Selecting previously unselected package mpv.
(Reading database ... 103969 files and directories currently installed.)
Preparing to unpack mpv_0.14.0_armhf.deb ...
Unpacking mpv (1:0.14.0) ...
dpkg: dependency problems prevent configuration of mpv:
mpv depends on libsmbclient (>= 2:4.0.3+dfsg1); however:
Package libsmbclient:armhf is not installed.
dpkg: error processing package mpv (--install):
dependency problems - leaving unconfigured
Processing triggers for gnome-menus (3.10.1-0ubuntu2) ...
Processing triggers for desktop-file-utils (0.22-1ubuntu1) ...
Processing triggers for mime-support (3.54ubuntu1.1) ...
Processing triggers for hicolor-icon-theme (0.13-1) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Errors were encountered while processing:
mpv